## BEATCALC:  Beat the Calculator!

Back to Calculation Tips & Tricks

 From B. Lee Clay

Squaring Numbers

Multiplying Numbers

Dividing Numbers

1. any by 0.125
2. 2 digits by 1 1/9
3. 2 digits by 1 1/8
4. 2 digits by 1 1/7
5. 2 digits by 1 1/6
6. 2 digits by 1 1/5
7. 2 digits by 1 1/4
8. 2 digits by 1 2/7
9. 2 digits by 1 1/3
10. 2 digits by 1 2/5
11. 2 digits by 1 3/7
12. 2 digits by 1 1/2
13. 2 digits by 1 3/5
14. 2 digits by 1 2/3
15. 2 digits by 1 3/4
16. 2 digits by 1 4/5
17. 2 digits by 2 2/9
18. 2 digits by 2 1/4
19. 2 digits by 2 1/3
20. 2,3 digits by 2 1/2
21. 2 digits by 2 2/3
22. 2 digits by 2 6/7
23. 2 digits by 3 1/8
24. 2,3 digits by 3 1/3
25. 2 digits by 3 1/2
26. 2 digits by 3 4/7
27. 2 digits by 4 1/6
28. 2 digits by 4 2/7
29. 2 digits by 4 4/9
30. 2 digits by 4 1/2
31. 2 digits by 5
32. 2 digits by 5 5/7
33. 2 digits by 6 1/4
34. 2 digits by 6 2/3
35. 2 digits by 7 1/7
36. 2 digits by 7 1/2
37. 2 digits by 8 1/3
38. 2 digits by 8 4/7
39. 2 digits by 12 1/2
40. 2 digits by 15
41. 2,3 digits by 16 2/3
42. 2,3 digits by 25
43. 2,3 digits by 33 1/3
44. 2,3 digits by 35
45. 2 digits by 37 1/2
46. 2 digits by 40
47. 2 digits by 45
48. 2 digits by 50
49. 2 digits by 62 1/2
50. 2 digits by 66 2/3
51. 2,3 digits by 75
52. 2 digits by 83 1/3
53. 2 digits by 87 1/2
54. 2 digits by 125
55. 2 digits by 166 2/3
56. 2 digits by 250
57. 2,3 digits by 333 1/3
58. 2 digits by 375
59. 2 digits by 625
60. 2 digits by 875
61. 3 digits rep./37+41
62. 6 digits rep. by 15873
63. 6 digits rep. by 7, then 13
64. 6 digits rep. by 13, then 11
65. 6 digits rep. by 7,11,13, subtract 101
66. 6 digits rep. by 37037 x 5
67. mixed numbers by 2
68. diff. of squares of 2 consec. 2-digit numbers
69. diff. of squares of 2 different 2-digit numbers
70. sqrt of squares of 2-digit numbers ending in 1
71. sqrt of perfect squares ending in 5

Subtracting Numbers

Finding Percents

Calculation
Practice Exercises

Full List

### Dividing a repeating 6-digit number by 7,                 then by 13

1. Select a 3-digit number.
2. Repeat these digits to make a 6-digit number.
3. Divide these 6 digits by 7, then by 13.
4. The answer is 11 times the first three digits!

#### Example:

1. If the 3-digit number selected is 234:
2. The 6-digit number is 234234.
3. Divide by 7, then by 13: multiply by 11
- to multiply 234 by 11, work right to left:
last digit on right = _ _ _ 4
next digit to left = 3 + 4 = 7: _ _ 7 _
next digit to left = 2 + 3 = 5: _ 5 _ _
last digit on left = 2 _ _ _
4. So 234234 divided by 7, then 13 is 2574.

See the pattern?

1. If the 3-digit number selected is 461:
2. The 6-digit number is 461461.
3. Divide by 7, then by 13: multiply by 11
- to multiply 461 by 11, work right to left:
last digit on right = _ _ _ 1
next digit to left = 6 + 1 = 7: _ _ 7 _
next digit to left = 4 + 6 = 10: _ 0 _ _
last digit on left = 4 + 1(carry) = 5: 5 _ _ _
4. So 461461 divided by 7, then 13 is 5071.

Practice multiplying by 11 - this process works for multiplying any number by 11.